For those of you who haven't committed to using a tripod regularly yet, here's some things to think about:
1) I don't know a single experienced photographer who uses a tripod with braces from the centre column to the legs, and most prevent the legs from swinging out for low work and irregular terrain and special situations.
2) likewise the use of anything but a ball head unless you are shooting large format - virtually all of us have converted over to ball heads of various designs and prices.
3) a tripod that goes to at least nipple height without the head and without raising the centre column is essential for a normal use tripod, though you may wish to compromise on a lightweight travel pod.
4) if you do a lot of stitching, you need something to level the rotation of the ball head - I use a leveller from Manfrotto on my Gitzo tripod, works really well.
5) number of sections really depends on quality of construction - lots of people decry 4 section legs but that's what I use and that extra height is sometimes very handy.
6) there are a few times that I have missed the ability to reach out horizontally, say over a wall and then shoot down, so there is definitely something to be said for the new manfrotto and other tripods that have swinging or positionable centre columns.
7) some say that you should never use a centre column becuase it isn't steady, but I have several portfolio images in which it was useful or even essential.
8) Carbon fibre is nice, but hardly essential. Wood can be good too and sure repairs a lot easier after jambing a leg in the car door. For a long time I used a Berlebach tripod with good results, though once I switched to dSLR's and a tall ballhead, it wasn't as stable beween the centre column and the head as I'd like. The swivelling centre post (essentially a ball joint with a hole in the middle for the centre post) was a great idea. I have even thought of getting a new centre column with a more solid top for the ball head. That tripod took abuse no metal or carbon fibre tripod would stand.
9) little spikes on tripod feet really don't do much for me - if the tripod isn't stiff enough to stand on ice on it's own, you have too loose a tripod. Big spikes like the Zone VI tripod used to have serve their function, but soft marshy ground isn't going to be fixed by any spike less than 10 feet long, so I don't consider spikes essential and I don't have them on my Gitzo.
10) quick release heads are nice, and for a dSLR, an L bracket is wonderful - but not cheap - Manfrotto make some nice inexpensive ball heads with quick release plates, and they don't have the problem of the camera sliding out of the plate holder because of being two instead of three dimensionally held. Mind you, my really right stuff lever release clamp has never ever let go and there's something about a clamp in which you can see from it's position that it's on - which you can't with a rotating knob. With knobs, I just get a bit paranoid and check frequently - never lost a camera yet and I do carry the 1Ds2 over my shoulder on the end of the tripod.